A built-up desk lamp, comprised of a lamp holder supported on a stand by a supporting frame for holding a lamp bulb, wherein the supporting frame is comprised of a plurality of frame sections flexibly adjusted into a desired length; the stand is comprised of a bottom shell connected with an upper shell for holding a connector, which bottom shell has a plurality of projecting strips respectively fastened in a plurality of retainer plates made on the upper shell and a lug connected to a bolt hole on the upper shell by a screw, which connector has one end inserted in a block on the inside of the upper shell and an opposite end connected to a power supply; the lamp holder is comprised of an upper shade connected with a bottom shade, which bottom shade has a plurality of hooks respectively hooked in a plurality of recesses on the upper shade, permitting the upper shade to be conveniently fixedly secured thereto by screws.